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Basic Radiation

February 2006

Saudi A

rabia : info_ksa@m

agusintl.comU

.A.E

: info_uae@m

agusintl.com

D I S T R I B U T O R

Saudi Arabia : [email protected] : [email protected]

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Topics

• Introduction to Radiation• Types of Radiation• How Radiation Interacts

with the Environment• Radiation Safety• Why We Need to Measure Radiation

Today

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Introduction to Radiation

• Radiation can be non-ionizing or ionizing• Non-ionizing radiation is generally a low

energy electromagnetic wave– Sunlight– Radio waves– Microwaves– Infrared waves

• Mostly harmless

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tionIonizing Radiation

• Ionizing (nuclear) radiation has enough energy to ionize the atoms and molecules it interacts with– Particles: alpha, beta, neutron– Waves: gamma

• Because it can ionize, it can cause biological damage

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tion • Ionizing Radiation is all around us

– We are constantly exposed to low levels of radiation from outer space, the earth, and medical treatments

– Low levels of naturally occurring radioactive material are in our environment, the food we eat, and in many consumer products

– Some consumer products also contain small amounts of man-made radioactive material

– However, exposure to large doses of radiation is definitely not desirable

– Most of your annual dose of radiation comes from Radon gas in your house!

Introduction to Radiation

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tionTypes of Radiation

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The Atom

Particle Location Charge Relative MassProton Nucleus

Nucleus

Orbit

+1 1Neutron neutral 1

Electron -1 1/1837

Carbon-12:• 6 Protons• 6 Neutrons• 6 Electrons

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The Atom

Particle Determines…Proton Element

Isotope

Ion

Chemical & physical propertiesNeutron Radioactivity

Electron Some bonding & interaction

Carbon-12:• 6 Protons• 6 Neutrons• 6 Electrons

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tion • Certain atoms are radioactive because

their nuclei are unstable– They have too few or too many neutrons, which

creates an imbalance

• To get stable, the atom “decays” and transforms into a new atom by emitting radiation in 4 forms:– Alpha particle (α)

– Beta particle (β)

– Gamma wave (γ)

– Neutron particle (n)

• Sometimes the new atom is also unstable, and it decays too, creating a “decay chain”

UCRL-PRES-149818. Understanding Radiation and it’s Effects.

Unstable Atoms Decay

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Source Activity

• The number of decays per unit time tell us how radioactive a source is. This is called activity.

• Measured in Curies (Ci) or Becquerels(Bq)– 1 Becquerel = 1 Bq = 1 decay per second– 1 Curie = 1 Ci = 3.7 x 1010 Bq– 1 Ci = the activity of 1 gram of Radium-226

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tion • The half life of a radioactive material tells us how

quickly it decays away• Half life = how long it takes for ½ of the

radioactive atoms in a sample to decay away• Measured in units of time• Some examples:

– Some natural isotopes (like Uranium and Thorium) have half lives that are billions of years

– Most medical isotopes (like Technicium-99m) last only a few days


Half Life

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tion • A +2 charged helium nucleus with 2

protons and 2 neutrons• Relatively heavy particle with a big charge• Travels 2-5 cm in air• Stopped by a piece of paper, or the top

layer of your skin• Difficult to detect • Dangerous if inhaled– will cause localized

severe damage to a thin layer of tissue in the lungs and respiratory tract- possible precursor to lung cancer

• Radioactive “beach ball”

Alpha Decay

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Beta Decay

• Negatively (or positively) charged electron• Relatively light particle, but still charged• Travels ~10 meters in air• Stopped by aluminum foil, glass plate or

2.5 cm of virtually anything• Difficult to detect• Dangerous if inhaled– will cause localized

severe damage to a thin layer of tissue in the lungs and respiratory tract- possible precursor to lung cancer

• Radioactive “golf ball”

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tion • Energetic electromagnetic wave (photon)

with no charge• Travels many kilometers/miles in air• Stopped by lead or concrete 10+ cm thick• Relatively easy to detect and direct

exposure is likely• Normal to be exposed to small amounts

everyday from ground radiation and cosmic rays

• γ rays vs. x-rays– γ rays are emitted from the nucleus of an atom– X-rays are emitted from the orbital electrons of

an atom• Radioactive

“9mm bullet”

Gamma Decay

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tion Small, neutral particles (same size as a

proton)• Travels many kilometers in air• Stopped by 30+ cm of water, polyethylene

or paraffin– Spent fuel rods are stored in water

• Self-fissioning radioactive materials (Plutonium, Californium) give off neutrons

• Large doses can do significant damage to people

Neutron “Decay”

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tionTypes of Radiation

Type of Radiation Physical Structure Travel Distance in Air &

Means of Attenuation

Alpha Particles

Positively charged Helium nucleus (2 protons & 2 neutrons)

~1-2 inchesStopped by a single sheet of paper

Beta Particles

Positively or negatively charged electrons

~30 feetStopped by aluminum foil, glass plate, ~1 inch of anything

Gamma Rays

(Photons)

Neutral, energetic electromagnetic wave

Many milesStopped by thick lead (4 inches) or very thick concrete

NeutronsSmall, neutral particles with mass very near a proton

Many milesStopped by 12 inches of water, polyethylene, paraffin

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What is a “Dose” of Radiation?

• When radiation hits your body, and it’s energy is transferred to your tissue, you have received a dose of radiation.

• The more energy deposited, the higher your dose.

• Measured in Roentgen Equivalent Man(rem) or sieverts (Sv – SI unit)

• Rads and Roentgens (R) are similar units that are often equated to the rem.

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Radiation Safety

• The fundamental principle of radiation safety is that radiation exposures should be maintained As Low As Reasonably Achievable (ALARA).

• The three factors influencing radiation dose are:– Time– Distance– Shielding

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tion • The less time you’re exposed, the

less exposure you get• Dose = Dose Rate x Time• If you want to limit your exposure to

100 μRem and the source is 200 μRem/hr then only stay near the source for 30 minutes:

200 µRem/hr x 0.5 hr = 100 µRem

• Limit your time near the radiation source!

ALARA - Time

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tion • The farther away from the source you are, the

weaker the source is to you• Exposure levels are based upon the inverse

square law

• Increase the distance between you and the source!

ALARA - Distance

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tion • Shielding can stop the radiation from

hitting you• Exposure levels can be reduced greatly by

putting shielding between yourself and the radiation source– α can be absorbed by a piece of paper– β can be absorbed by 1” of aluminum or glass– γ can be absorbed by thick lead shields– n can be absorbed by paraffin, water,

polyethylene• Increase the amount of shielding

material between you and the source!

ALARA - Shielding

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Shielding/Attenuating Radiation

α

Paper

Glass, thin m

etal

Lead, C

oncreteα

α

α

ββ

β

β

γ

γγγ

Water,

Polyethylene

nnnn

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Shielding/Attenuating Radiation

α

Paper

Glass, thin m

etal

Lead, C

oncreteβ

γ Water,

Polyethylene

η

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tion • Another danger to the body is through the entry

of radioactive substances into the body rather than a short external exposure to radiation.

• Routes of entry to the body:1. Air Lungs , e.g. Radon Gas2. Food, drinking water Mouth Bloodstream, GI

tract3. Body Cuts Bloodstream

• Once in the body, the radioactive substance is the “gift that keeps on giving”

• However, the human body is very resilient, and has very efficient repair mechanisms to deal with small, normal amounts of radiation damage

Radiation Safety

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Irradiated or Contaminated?

• Irradiated– You are “irradiated” when radiation hits you– You do NOT become radioactive when you

are irradiated– Some forms of radiation CAN penetrate

personal protective clothing

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Irradiated or Contaminated?

• Contaminated– Contamination is radioactive dirt– You can become contaminated by touching

radioactive dirt– Contamination can be washed off like any dirt– Personal protective equipment can protect

people from contamination

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Typical Yearly Radiation Dosage

* Understanding Radiation: Bjorn Wahlstrom

Average Annual Radiation Dosage*

Radon in homes (~240 mRem)

Medicine (70 mRem)

Natural radiation from ground (50mRem)Natural activity in body (40 mRem)

Cosmic radiation (30 mRem)

Others (10 mRem)

• Total average annual dosage: 440 mRem

• Annual dosage can be increased by smoking, living at higher elevations, living in a brick, stone or concrete house, flying, plutonium-powered pacemakers, watching TV, medical x-rays.

• Calculate your own exposure at: http://www.epa.gov/radiation/students/calculate.html

http://www.epa.gov/radiation/students/calculate.html

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Common Doses in Everyday Life**

DosageμSv μrem

Cause of Dose

100 10,000 Average annual chest x-ray exposure

2000 200,000 Annual exposure from radon gas in homes

810 81,000 Annual background radiation exposure at high elevation (Denver)

14,000 1,400,000 Gastro-intestinal Barium x-ray (GI series)

** Hazardous Materials Air Monitoring and Detection Devices: Chris Hawley

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Important Dose Limits**

Dose Rate Limit

μSv μrem

Description of Limit

10 1,000 Limit for normal public activities50,000 5,000,000 Limit for all activities

100,000 10,000,000(10 rem)

Limit for protecting valuable property

250,000 25,000,000(25 rem)

Limit for lifesaving or protection of large populations

>250K >25,000,000 (>25 rem)

Limit for lifesaving or protection of large populations only on a voluntary basis for persons aware of the risks

** Hazardous Materials Air Monitoring and Detection Devices: Chris Hawley

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Acute Radiation Doses

Dose (Rads*) Effects25 – 50

(~25,000,000 – 50,000,000 μrem)First sign of physical effects –drop in white blood cell count

100(~100,000,000 μrem)

Vomiting within several hours of exposure

320 – 360(~ 320,000,000 – 360,000,000 μrem)

~50% die within 60 days with minimal supportive care

480 – 540(~480,000,000 – 540,000,000 μrem)

~50% die within 60 day with supportive care

1,000(~ 1,000,000,000 μrem)

~100% die within 30 days

*1 Rad can be approximated to 1 rem = 1,000,000 μrem = for common external exposures

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Why Detect Radiation Today?

• Medicine– Imaging– Cancer treatment and therapy

• Industrial– Imaging– Gauges

• Power• Agriculture• Radiological terrorism

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Radiological Terrorism

• Radiological Terrorism is a real and possible threat– High psychological/emotional impact– High economic impact– Many devices are easy to build– Al Qaeda has threatened radiological terrorism– It’s already being done

• Improvised Nuclear Device• Radiological Dispersion Devices (RDDs)• Radiation detection covers two letters of

CBRNE preparedness: Radiological and Nuclear

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Radiological Terrorism

• Nuclear warheads use special nuclear materials and fission or fusion to create a nuclear payload

• Plutonium 239 and Uranium 235 are the special nuclear materials used in weaponry

• Medical and industrial radioactive materials CANNOT produce a nuclear warhead– they can only be used to contaminate!!!

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tionThreat Comparison

Sev

erity

of i

ncid

ent

Probability of incident

Stolen nuclear weapon

Improvised nuclear device

RDD

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Radiological Dispersion Devices

• Radiological dispersion devices (RDDs) can take two main forms:– A dirty bomb- a core of radiological material

wrapped in conventional explosives– A simple radioactive source left discretely in a

public place• The key to these devices is NOT

destruction- it’s fear and contamination. It is a psychological and “denial of service” attack on the economy.

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Making an RDD

• All you need is radiological material• Optional: Explosives• Orphan sources

– Radiological materials are used everyday in a variety of applications

– Some sources are lost, forgotten, or disposed of improperly – Orphan sources

– Over 200,000 available today

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Example of an RDD

• 1 pound of HE, two patient doses of liquid Technetium-99m (Tc-99m) near the HE

• Weather: 30 degrees F, sunny, light winds with gusts of 20 mph

• Tc-99m chosen due to level of radioactivity (high), short half-life, environmentally safe daughters, and availability

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Example of an RDD

• Contamination measured at 4 times background

• Due to short half-life, Tc-99m decayed to non-hazardous daughters within 60 hours

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Threats

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Radioisotope Half-Life

Alpha Emission

Beta Emission

Gamma Emission

Neutron Emission

Detect with GammaRAE

II?Cobalt-60 5.3 yrs No Low Energy High

EnergyNo Yes

Cesium-137 30 yrs No Low Energy Delayed High

Energy

No Yes

Iridium-192 74 days No High Energy High Energy

No Yes

Stronium-90 29 yrs No High Energy No No Yes

Americium-241 433 years

High Energy

No Low Energy No Yes

Californium-252 2.6 years

High Energy

No Low Energy Yes (Spont. Fission)

Yes

Plutonium-238 88 yrs High Energy

No Low Energy Yes (Spont. Fission)

Yes

Source: “Commercial Radioactive Sources: Surveying the Security Risks,”Monterey Institute of International Studies, 1/2003

Commonly Orphaned IsotopesCommonly Available Isotopes That Are Suitable For RDDs

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“Innocent” Sources

• Innocent Source: a radioactive source seen in typical day to day operations– May be the source of “false” alarms– Could be used to shield/disguise a real source

• Ship/truckloads of tile, bricks• Containers of bananas, fertilizer containing

potassium• Patients who have received radioactive

iodine, barium or other nuclear medicine treatments

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Summary

• Radioactivity is all around us– There are 4 types of radiation: alpha, beta,

gamma, and neutron• Radiation is used in many applications in

everyday life• Radiation can also be used for

malicious/terrorist acts• Knowing more about radiation can help to

better understand the threat, and reduce the chances of an occurance

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Additional Slides

• Additional Slides

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Mishaps

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Terrorist Attacks

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RDDs

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Material Attacks

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Material Theft

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Specific Activity

• Specific Activity refers to the activity of 1 gramof a radioactive material

• Different isotopes have different specific activities.

• The longer the half-life of the isotope, the lower the specific activity of the isotope.– 1 gram of cobalt-60 has

the same activity as 3300 metric tons of uranium-238

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Uranium billions of years

Natural uranium is comprised of several different isotopes. When enriched in the isotope of U-235, it’s used to power nuclear reactor or nuclear weapons.

Carbon-14 5730 y Found in nature from cosmic interactions, used to“carbon date” artifacts and as radiolabel for detectionof tumors.

Cesium-137 30.2 y Blood irradiator, tumor treatment through externalexposure. Also used for industrial radiography.

Hydrogen-3 12.3 y Labeling biological tracers.

Iridium-192 74 d Implants or "seeds" for treatment of cancer. Alsoused for industrial radiography.

Technicium-99m

6 h Brain, heart, liver, lungs, bones,thyroid, and kidney, regional cerebral blood flowimaging.

Some Isotopes & Their Half-Lives


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Exposure

• Exposure: how much radiation “hits” an object (or person)

• Measured in Roentgens (R)• Visualize the amount of light emitted by the sun

that hits you while sitting on the beach

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tion • Absorbed dose: how much energy is imparted

on/transferred to the object by the radiation• Measured in Rads (Radiation Absorbed Dose)

or Grays (Gy)– Units of energy/mass– 1 Gy = 100 rad

• Imagine how much your skin heats up from the sunlight hitting it

Absorbed Dose

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Biologically Equivalent Dose

• Biologically equivalent dose: Radiation-weighted dose to quantify the effects of radiation on biological tissue

• Measured in Roentgen Equivalent Man (rem) or Sieverts (Sv)– 1 Sv = 100 rem

• Imagine how sunburnt you get from sitting out in the sun

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How Radiation Interacts

• Imagine you’re relaxing on the beach on a sunny day:– The amount of light the sun emits is the

“activity” of the sun– The amount of light that hits your skin is your

exposure– The amount your skin heats up is your

“absorbed dose”– The amount of sunburn you get is your

“biologically equivalent dose”

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Radiation Units

Type Unit Definition

Source activity Curie (Ci)Becquerel (Bq)

3.7 x 1010 disintegrations/second1 disintegration per second

Exposure (X & gamma rays)

Absorbed dose

Biologically equivalent

dose

Roentgen (R)2.58 x 10-4 Coulombs/Kg in dry air at STP1 Coulomb per 1cc dry air at STP

radGray (Gy)

0.01 J /Kg1 J /Kg 1Gy = 100 Rad

RemSievert (Sv)

QFR x (dose in rad)QFG x (dose in Gray)

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Radiation Equivalents

Rem Millirem(mrem)

Microrem(µrem)

1 1,000 1,000,000

0.1 100 100,000

0.01 10 10,000

0.001 1 1,000

0.0001 0.1 100

0.00001 0.01 10

0.000001 0.001 1

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Radiation Equivalents

Unit Measured Quantity

Rad, Grey (Gy) Absorbed Dose

Rem, Sievert (Sv) Biologically Equivalent Dose

Unit Equivalents

100 Rem 1 Sv1 Rem 10 mSv (millisievert)1 mrem (millirem) 10 μSv (microsievert)

1 μrem (microrem) 0.01 μSv

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Radioactive Contamination


• Radiation cannot make you radioactive*

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Radioactive Contamination


• Radioactive contamination can stick to clothes & skin. It can be washed away like any dirt*.

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Radiation has had a bad publicist!

•• When most people think of radiation, When most people think of radiation, they think of the mushroom cloud they think of the mushroom cloud from the atomic bomb tests in the from the atomic bomb tests in the 1940’s & 50’s.1940’s & 50’s.

•• If people thought the same way about If people thought the same way about electricity, their first image would be electricity, their first image would be of the electric chair instead of the of the electric chair instead of the light bulb!light bulb!

•• The goal of this presentation is to The goal of this presentation is to demystify radiationdemystify radiation

1952, Operation Ivy, “Mike” H-Bomb

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